Holley Carb swap

[zeus87gn]

I have the 87 Wrangler with the 4.2L, 5-speed. My original carter carb pos went south sime time ago and I decided to go with the Holley 350cfm straight 2bbl and an adapter plate.

Has anyone ever done the carter to Holley swap?
If so, what were your solutions to get it running correctly?

I have done this swap and have been doing adjustments for some time trying to get the stumble out and have had no success.

Any and all help is appreciated.

TIA

[FarrellX]

sorry this is no help, but i bought my jeep with that exact carb. couldnt compare it to the stock carb, but compared to other cars with carbs, it seems to run much better. if my carb died though..id just go all out with fuel injection. but thats just me

[zeus87gn]

Thanks for the response.
I wish I had the money for the FI kit, but $2700 is hard to come by right now.
Compared to the stock carb, it's a massive improvement. I swear I get better mileage now. I just had to have a custom adapter plate made to solve a vaccum leak and it helped but didn't solve the problem.

Have you ever been into the carb?
Do you know what size jets and power valve you have?
How about injector nozzle size?

I'm hoping it's just down to the right combo of the three to get rid of the stumble.

[zeus87gn]

TTT

Anyone else?

[zeus87gn]

Noone?

Surely there is someone in this fine country of ours that has doe this before that can give me some assistance.

Any and all help/comments are appreicated/welcomed.

[PRCE7]

Originally Posted by zeus87gn

Thanks for the response.
I wish I had the money for the FI kit, but $2700 is hard to come by right now.
Compared to the stock carb, it's a massive improvement. I swear I get better mileage now. I just had to have a custom adapter plate made to solve a vaccum leak and it helped but didn't solve the problem.

Have you ever been into the carb?
Do you know what size jets and power valve you have?
How about injector nozzle size?

I'm hoping it's just down to the right combo of the three to get rid of the stumble.

According to AFI you can pick up a "Complete AMC Throttle Body Fuel Injection System" for 1295.00

http://www.affordable-fuel-injection.com/amc-system.htm

If my weber ever goes out that's what I'm shooting for.

[zeus87gn]

Well, in case anyone ever wants to know, I did FINALLY get rid of my stumble. Ol Frankenstein is running like a champ, ever when cold.

- custom fab adaptor plate (no cheapo universal)
- size 58 jets
- 10.5" power valve (22" vaccum at idle)
- 25cc accelerator pump (with taught adjustment screw)
- and I believe a #42 injector nozzle but I may try and size it down and see how it runs.


Yes, this is on a stock 4.2l rebuild.
Runs like a small V8 in the warm months

[Richmond88yj]

Originally Posted by zeus87gn

Well, in case anyone ever wants to know, I did FINALLY get rid of my stumble. Ol Frankenstein is running like a champ, ever when cold.

- custom fab adaptor plate (no cheapo universal)
- size 58 jets
- 10.5" power valve (22" vaccum at idle)
- 25cc accelerator pump (with taught adjustment screw)
- and I believe a #42 injector nozzle but I may try and size it down and see how it runs.


Yes, this is on a stock 4.2l rebuild.
Runs like a small V8 in the warm months

So what actually solved the stumble? The adapter plate curing the vac leak?

[zeus87gn]

Originally Posted by Richmond 88 YJ

So what actually solved the stumble? The adapter plate curing the vac leak?

It was really the whole combination/setup.

I talked to Holley tech support after making many adjustments that never really did anything. Came to the conclusion that it was indeed a lean stumble. The engine would run out of gas at a certain point in pedal travel (butterfly poistion vs engine vaccum). Adjusted the powervalve to my vaccum reading and corrected the accelerator pump & linkage (big help here!). The jet size came along in the middle of all this by looking at spark plugs and discussing it with another board member.

The adaptor plate issue was always a concen to me so I just decided to spend the money to eliminate any possibility of a problem. I changed it straight out without any other adjustments and could tell a difference in operation. It was a wonderful addition as the shop that cut it for me beveled the throats from the Holley to the fcty manifold...made it out of 5/8 thk plate.

BUT it wasn't until after I changed the plate that I could figure out the other adjustments. So yes, the plate put me on the path to success.

Strange that I could never find the leak....

[jeepdrvr101]

I have had problems with my holley carb since I put it in, I think mine is a 250, but do not remember. Mabye I'll try a new adapter plate, and see where I go from there.

Mike

[zeus87gn]

Originally Posted by jeepdrvr101

I have had problems with my holley carb since I put it in, I think mine is a 250, but do not remember. Mabye I'll try a new adapter plate, and see where I go from there.

Mike

If you have the aftermarket version that has the same bolt flange as the MC2xxx, it is a 350. It's the smallest universal carb they make.

If you have the adaptor plate that has slots in the bolt pattern, it's leaking. That is what I replaced.

I have a new digital camera on order, should be in tomorrow. I'll post pics of it. You guys have to see this plate they made for me. It's fabulous. Even the guys at Salvage Jeep thought it was great.

[pyro9862]

Originally Posted by jeepdrvr101

I have had problems with my holley carb since I put it in, I think mine is a 250, but do not remember. Mabye I'll try a new adapter plate, and see where I go from there.

Mike

Spray starter fluid around the base of the adapter plate and see if the idle changes. I had the same problem with my MC2100 so I remounted it with a new gasket and some silicone that solved part of my problem.

Originally Posted by zeus87gn

You guys have to see this plate they made for me. It's fabulous. Even the guys at Salvage Jeep thought it was great.

Where did you get the plate?

[jeepdrvr101]

Originally Posted by pyro9862

Spray starter fluid around the base of the adapter plate and see if the idle changes. I had the same problem with my MC2100 so I remounted it with a new gasket and some silicone that solved part of my problem.



Where did you get the plate?

I don't know a buddy of mine worked at one of the local jeep dealerships as the shop supv. he did the original work on it for me, but now he is gone so I can't even ask him anything about it.

Mike

[zeus87gn]

Ok, I know this has been a long time in coming but I finally got some pics of this custom fabricated plate. This is actually the second one, the first is on my motor. Wizard has been waiting on this one!

I have also added a fuel pressure regulator.
More explanation on this later.
It is definitely an added bonus.

[zeus87gn]

Finally, a moment to breathe...

This has been quite the nice addition to my setup.
Stinky exhaust virtually eliminated.
No more black spots on startup (spitting from the tailpipe).
Smoother operation.
Better tuning response when adjusting the mixture.
Just all around one d@mn good thing to have done.
I highly recommend this to anyone running this carb.
I presently have it set on 3-1/2.
4 was starting to get rich again, 3 made it lack some power.
I'm still experimenting with it.

I contacted Holley about this and they agreed it may be a good thing as the Holley is only made to run on 6-1/2 psi. I have read the stock FP on the old 4.2's puts out about 7 to 8 psi.